Ultraviolet absorber composition and resin composition stabilized therewith

ABSTRACT

The present invention is directed to an ultraviolet absorber composition which is formed by melt-mixing a compound (A) represented by formula (I):                  
 
and a resin stabilizer (B) selected from the group consisting of a phenolic antioxidant (b-1), a phosphorus-containing antioxidant (b-2), a hindered amine stabilizer (b-3), and an ultraviolet absorber (b-4) other than the compound (A), at a mass ratio (A)/(B) of 95/5 to 50/50. The composition has excellent compatibility with synthetic resins and provides a stabilized synthetic resin molding.

This application is the US national phase of international applicationPCT/JP02/05597 filed 6 Jun. 2002 which desinated the U.S., the entirecontent of which is hereby incorporated by reference in thisapplication.

TECHNICAL FIELD

The present invention relates to an ultraviolet absorber compositionwhich is produced by melt-mixing a benzotriazole compound having aspecific structure and a resin stabilizer other than the benzotriazolecompound and which has a low melting temperature and excellentcompatibility with a resin. The invention also relates to a syntheticresin composition stabilized by the ultraviolet absorber composition.

BACKGROUND ART

Conventionally, a variety of synthetic resins have been applied,according to their chemical and physical characteristics, to uses suchas building materials, agricultural materials, miscellaneous goods,automobile parts, housings of electric appliances, coatings, andpackaging materials.

Without resin stabilizers, most synthetic resins are deteriorated byheat or light. Therefore, an antioxidant such as a phenolic antioxidant,a phosphorus antioxidant, or a sulfur antioxidant; an ultravioletabsorber; or a hindered amine stabilizer has been added to the syntheticresins.

Conventionally, in order to stabilize a resin, a plurality of additiveshave also been added to the resin depending on the purpose ofstabilization. Combination of such additives has been widely known toproduce synergistic effects. For example, a combination of a phenolicantioxidant and a phosphorus antioxidant imparts heat resistance to theresin, and a combination of an ultraviolet absorber and a hindered aminestabilizer imparts weather resistance to the resin.

Among these additives,2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol is known to serveas an excellent ultraviolet absorber, as disclosed in Japanese PatentApplication Laid-Open (kokai) No. 61-118373. Japanese Patent ApplicationLaid-Open (kokai) Nos. 61-113649, 61-113667, 61-163954, 62-225554,62-146951, 62-172058, 63-10653, etc. disclose uses of the phenolcompound in a variety of resins.

However, 2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol has poorcompatibility with certain types of resin, such as polyolefin resin.When the compound is added to such a resin, the compound migrates to thesurface of the resin products (i.e., exhibits blooming), therebyimpairing the commercial value of the resin products. Therefore,limitations have been imposed on the type of resin to which the compoundis added.

Thus, demand has arisen for improving the compatibility of2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol—an excellentultraviolet absorber—to a resin, thereby enabling addition of thecompound to a resin for which highly stabilizing effect is required.

DISCLOSURE OF THE INVENTION

The present inventors have carried out extensive studies in an attemptto meet the aforementioned demand, and have found that an ultravioletabsorber composition produced by melt-mixing2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol and a resinadditive other than the phenol compound has excellent compatibility witha resin, and that a stabilized resin composition which provides productswith less blooming can be produced from the ultraviolet absorbercomposition. The present invention has been accomplished on the basis ofthese findings.

Accordingly, in a first mode of the present invention, there is providedan ultraviolet absorber composition which is formed by melt-mixing acompound (A) represented by the following formula (I):

and a resin stabilizer (B) selected from the group consisting of aphenolic antioxidant (b-1), a phosphorus-containing antioxidant (b-2), ahindered amine stabilizer (b-3), and an ultraviolet absorber (b-4) otherthan the compound (A), at a mass ratio (A)/(B) of 95/5 to 50/50.

A second mode of the present invention is drawn to a specificultraviolet absorber composition of the first mode, wherein the resinstabilizer (B) is the ultraviolet absorber (b-4) other than the compound(A).

A third mode of the present invention is drawn to a specific ultravioletabsorber composition of the second mode, wherein the ultravioletabsorber (b-4) other than the compound (A) is a benzotriazoleultraviolet absorber.

A fourth mode of the present invention is drawn to a specificultraviolet absorber composition of the third mode, wherein thebenzotriazole ultraviolet absorber is a compound represented by thefollowing formula (II).

In a fifth mode of the present invention, there is provided a syntheticresin composition comprising a synthetic resin and an ultravioletabsorber composition as recited in relation to any of the first tofourth modes.

A sixth mode of the present invention is drawn to a specific syntheticresin composition of the fifth mode, wherein the synthetic resin is apolyolefin resin.

BEST MODE FOR CARRYING OUT THE INVENTION

Modes for carrying out the present invention will next be described.

Examples of the phenolic antioxidant (b-1) used in the present inventioninclude 2,6-di-tert-butyl-p-cresol, 2,6-diphenyl-4-octadecyloxyphenol,distearyl (3,5-di-tert-butyl-4-hydroxybenzyl) phosphonate,1,6-hexamethylenebis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide],4,4′-thiobis(6-tert-butyl-m-cresol),2,2′-methylenebis(4-methyl-6-tert-butylphenol),2,2′-methylenebis(4-ethyl-6-tert-butylphenol),4,4′-butylidenebis(6-tert-butyl-m-cresol),2,2′-ethylidenebis(4,6-di-tert-butylphenol),2,2′-ethylidenebis(4-sec-butyl-6-tert-butylphenol),1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane,1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene,2-tert-butyl-4-methyl-6-(2-acryloyloxy-3-tert-butyl-5-methylbenzyl)phenol,stearyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate, thiodietyleneglycol bis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],1,6-hexamethylene bis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],bis[3,3-bis(4-hydroxy-3-tert-butylphenyl)butyric acid]glycol ester,bis[2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl]terephthalate,1,3,5-tris[(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyethyl]isocyanurate,tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionato]methane,3,9-bis[1,1-dimethyl-2-{(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane,and triethylene glycolbis[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate].

Examples of the phosphorus antioxidant (b-2) used in the presentinvention include trisnonylphenyl phosphite,tris(2,4-di-tert-butylphenyl) phosphite,tris[2-tert-butyl-4-(3-tert-butyl-4-hydroxy-5-methylphenylthio)-5-methylphenyl]phosphite,tridecyl phosphite, octyl diphenyl phosphite, di(decyl) monophenylphosphite, di(tridecyl)pentaerythritol diphosphite,di(nonylphenyl)pentaerythritol diphosphite,bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite,bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite,bis(2,4-dicumylphenyl)pentaerythritol diphosphite,tetra(tridecyl)isopropylidenediphenol diphosphite,tetra(tridecyl)-4,4′-n-butylidenebis(2-tert-butyl-5-metylphenol)diphosphite,hexa(tridecyl)-1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butanetriphosphite, tetrakis(2,4-di-tert-butylphenyl)biphenylenediphosphonite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide,2,2′-methylenebis(4,6-tert-butylphenyl)-2-ethylhexyl phosphite,2,2′-methylenebis(4,6-tert-butylphenyl)-octadecyl phosphite,2,2′-ethylidenebis(4,6-di-tert-butylphenyl)fluorophosphite,tris(2-[(2,4,8,10-tetrakis-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]ethyl)amine,and a phosphite of 2-ethyl-2-butylpropylene glycol and2,4,6-tri-tert-butylphenol.

Examples of the hindered amine stabilizer (b-3) used in the presentinvention include hindered amine compounds such as2,2,6,6-tetramethyl-4-piperidyl stearate,1,2,2,6,6-pentamethyl-4-piperidyl stearate,2,2,6,6-tetramethyl-4-piperidyl benzoate,bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate,tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butanetetracarboxylate,tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butanetetracarboxylate,bis(2,2,6,6-tetramethyl-4-piperidyl) di(tridecyl)1,2,3,4-butanetetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)di(tridecyl) 1,2,3,4-butanetetracarboxylate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-butyl-2-(3,5-di-tert-butyl-4-hydroxybenzyl)malonate,1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol/diethyl succinatecondensate,1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/dibromoethanecondensate,1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/2,4-dichloro-6-morpholino-s-triazinecondensate,1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/2,4-dichloro-6-tert-octylamino-s-triazinecondensate,1,5,8,12-tetrakis[2,4-bis(N-butyl-N-(2,2,6,6-tetramethyl-4-piperidyl)amino)-s-triazin-6-yl]-1,5,8,12-tetrazadodecane,1,5,8,12-tetrakis[2,4-bis(N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino)-s-triazin-6-yl]-1,5,8,12-tetrazadodecane,1,6,11-tris[2,4-bis(N-butyl-N-(2,2,6,6-tetramethyl-4-piperidyl)amino)-s-triazin-6-yl]aminoundecane,and1,6,11-tris[2,4-bis(N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino)-s-triazin-6-yl]aminoundecane.

Examples of the ultraviolet absorber (b-4) other than the compound (A)used in the present invention include 2-hydroxybenzophenone compoundssuch as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,2-hydroxy-4-octoxybenzophenone, and5,5′-methylenebis(2-hydroxy-4-methoxybenzophenone);2-(2′-hydroxyphenyl)benzotriazole compounds such as2-(2′-hydroxy-5′-methylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-dicumylphenyl)benzotriazole, and2-(2′-hydroxy-3′-tert-butyl-5′-carboxyphenyl)benzotriazole; benzoatessuch as phenyl salicylate, resorcinol monobenzoate,2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate,2,4-di-tert-amylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate; andhexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate; substituted oxanilidecompounds such as 2-ethyl-2′-ethoxyoxanilide and2-ethoxy-4′-dodecyloxanilide; cyanoacrylates such asethyl-α-cyano-β,β-diphenylacrylate andmethyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate; andtriaryltriazines such as2-(2-hydroxy-4-octoxyphenyl)-4,6-bis(2,4-di-tert-butylphenyl)-s-triazine,2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-s-triazine, and2-(2-hydroxy-4-propoxy-5-methylphenyl)-4,6-bis(2,4-di-tert-butylphenyl)-s-triazine.

The resin stabilizer (B) is added to a resin in a preferred amount,which varies in accordance with the type and use purpose of the resinand depending on the type of the resin stabilizer (i.e., antioxidant,hindered amine compound, or ultraviolet absorber). Thus, among resinstabilizers (B), the ultraviolet absorber (b-4) other than the compound(A) is preferably used, since the amount of the absorber (b-4)incorporated into the ultraviolet absorber composition to be added to aresin can be selected from a wide range. Among ultraviolet absorbers(b-4), a benzotriazole ultraviolet absorber, having high compatibilitywith the compound (A) during melt-mixing, is more preferred, with acompound represented by the following formula (II) being particularlypreferred, from the viewpoint of a remarkable blooming-preventioneffect.

In order to ensure both benefits of excellent ultraviolet absorbingperformance of the compound (A) and the effects—provided throughmelt-mixing, of lowering the melting temperature of the ultravioletabsorber composition and preventing blooming—the ratio of compound (A)to resin stabilizer (B) ((A)/(B)) by mass is controlled so as to fallwithin a range of 95/5 to 50/50, preferably 90/10 to 70/30.

Examples of synthetic resins to which the ultraviolet absorbercomposition of the present invention include homopolymers and copolymerof α-olein such as polypropylene, low-density polyethylene,linear-low-density polyethylene, high-density polyethylene,polybutene-1, poly(3-methylpentene), poly(4-methylpentene), andethylene-polyethylene copolymer; copolymers of α-olefins with apolyunsaturated compound such as conjugated or non-conjugated diene,acrylic acid, methacrylic acid, or vinyl acetate; linear polyesters andacid-modified polyesters such as polyethylene terephthalate,polyethylene terephthalate isophthalate, polyethylene terephthalatep-oxybenzoate, and polybutylen terephthalate; polyamides such aspolycaprolactam and polyhexamethyleneadipamide; polyimides; polystyrene;copolymers (e.g., AS resin, ABS resin, MBS resin, and heat-resistant ABSresin) of styrene and/or α-methylstyrene with a monomer (e.g., maleicanhydride, phenylmaleimide, methyl methacrylate, butadiene, oracrylonitrile); halogen-containing resins such as polyvinyl chloride,polyvinylidene chloride, chlorinated polyethylene, chlorinatedpolypropylene, polyvinylidene fluoride, chlorinated rubber, vinylchloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer,vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinylidenechloride-vinyl acetate terpolymer, vinyl chloride-acrylic estercopolymer, vinyl chloride-maleic ester copolymer, and vinylchloride-cyclohexylmaleimide copolymer; polymers of (meth)acrylic estersuch as methyl (meth)acrylate, ethyl (meth)acrylate, or octyl(meth)acrylate; thermoplastic resins such as polyether ketone, polyvinylacetate, polyvinyl formal, polyvinyl butyral, polyvinyl alcohol, linearor branched polycarbonate, petroleum resins, cumarone resins,polyphenylene oxide, polyphenylene sulfide, polyurethane, and celluloseresin; thermosetting resins such as epoxy resin, phenolic resin, urearesin, melamine resin, and unsaturated polyester resin; elastomers suchas polyisoprene rubber, polybutadiene rubber, butadiene-styrenecopolymer rubber, butadiene-acrylonitrile copolymer rubber,acrylonitrile-butadiene-styrene copolymer ethylene-α-olefin (e.g.,propylene or butene-1) copolymer rubber, andethylene-α-olefin-non-conjugated diene (e.g., ethylidenenorbornene orcyclopentadiene) terpolymer rubber; and silicone resins. Polymer alloysand blends of these resins and/or elastomers may also used.Particularly, the ultraviolet absorber composition of the presentinvention is suitably added to polyolefin resin, which per se has poorcompatibility with2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol.

To the synthetic resin composition of the present invention, otheradditives which are generally used in resins may be added in accordancewith needs. Examples of the additives include thioether antioxidants;nucleating agents such as a phosphate ester metal salt, benzylidenesorbitol, and a benzoic acid derivative metal salt; heavy metaldeactivators; fatty acid metal salts; hydrotalcite; fillers; pigments;dyes; fire-proofing agents; and processing aids.

No particular limitation is imposed on the method for producing theultraviolet absorber composition of the present invention. For example,the composition can be produced by heat-melting the compound (A) and theresin stabilizer (B) in a vessel in an inert atmosphere; transferringthe melt under stirring to an aluminum tray for cooling; and pulverizingthe cooled mixture by means of a flaker. Alternatively, the compositioncan be produced by dissolving the compound (A) and the resin stabilizer(B) in a solvent to form a uniform solution; removing the solvent fromthe solution at a temperature equal to or exceeding the meltingtemperature of the mixture to be produced through removal of thesolvent, to thereby form a melt mixture; and removing, cooling, andcrushing the mixture. The latter method, in which two components aredissolved in a solvent to form a solution, requires an additionalsolvent removal step and is not advantageous from an economicalviewpoint. However, the process can be performed at a comparatively lowtemperature, whereby coloring and decomposition of the compound (A) andthe resin stabilizer (B) by heat can be prevented.

No particular limitation is imposed on the method for incorporating thethus-produced ultraviolet absorber composition into a synthetic resin,and a method known per se for incorporating a stabilizer to a resin;e.g., mixing by means of a ribbon blender, a Henschel mixer, etc., canbe employed. An extruder or a Banbury mixer may also be used inaccordance with needs. Although the amount of the ultraviolet absorbercomposition incorporated into a synthetic resin varies in accordancewith the mass ratio (A)/(B) of the ultraviolet absorber composition,each component is used in an amount of 0.001 to 10 parts by mass basedon 100 parts by mass of the synthetic resin, preferably 0.05 to 5 partsby mass.

EXAMPLES

The present invention will next be described in more detail by way ofexamples, which should not be construed as limiting the inventionthereto.

Examples 1-1 to 1-7

Each sample compound (listed in Table 1) (5 g) and2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol (20 g) were mixedfor 30 seconds by means of a mixer, and the mixture was dissolved at180° C. in an aromatic hydrocarbon solvent (SOLVESSO® 150 solvent,product of ExxonMobil Chemical Company) (25 g). The solvent of thesolution was removed while the solution was maintained at 180° C., tothereby form a melt mixture. The thus-formed melt mixture wastransferred to an aluminum tray and cooled, and pulverized to a particlesize of 1 mm or less. The melting temperature of the pulverized productwas determined through visual observation. The results are shown inTable 1.

Comparative Examples 1-1 to 1-4

Each sample compound (listed in Table 1) (5 g) and2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol (20 g) were mixedfor 30 seconds by means of a mixer, to thereby yield a “physicallyprepared mixture.” The melting temperature of the mixture was determinedthrough visual observation. The results are shown in Table 1. Notably,in Comparative Examples, temperatures shown in the column labeled“Melting temperature of melt mixture” of Table 1 represent the meltingtemperatures of the two components of the physically prepared mixture.

TABLE 1 Melting point Melting temp. Sample of sample of melt compoundcompound mixture Examples 1-1 Phenol-1*¹ 50° C. 55–65° C. 1-2 Phenol-2*²115° C. 65–74° C. 1-3 Phosphorus-1*³ 183° C. 62–70° C. 1-4Phosphorus-2*⁴ 148° C. 64–71° C. 1-5 Phosphorus-3*⁵ 237° C. 72–78° C.1-6 HALS-1*⁶ 84° C. 60–71° C. 1-7 HALS-2*⁷ >65° C. 63–71° C. 1-8 UVA-1*⁸135–143° C. 66–73° C. 1-9 UVA-2*⁹ 102–105° C. 67–74° C. Comp. Examples1-1 Phenol-1*¹ 50° C.  50° C., 193° C. 1-2 Phosphorus-1*³ 183° C. 182°C., 195° C. 1-3 HALS-1*⁶ 84° C.  83° C., 194° C. 1-4 UVA-1*⁸ 135–143° C.   133–142° C.,     194° C. *¹stearyl(3,5-di-tert-butyl-4-hydroxyphenyl)propionate*²tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionato]methane*³tris(2,4-di-tert-butylphenyl) phosphite*⁴2,2’-methylenebis(4,6-tert-butylphenyl)-2-ethylhexyl phosphite*⁵bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite*⁶bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate*⁷tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl) butanetetracarboxylate*⁸2-(2’-hydroxy-3’,5’-dicumylphenyl)benzotriazole*⁹2-(2’-hydroxy-5’-tert-octylphenyl)benzotriazole

As is clear from Table 1, the melting point of2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol and that of theadded component were maintained when the two components were simplymixed. However, a composition exhibiting a low melting temperature wasformed by melt-mixing the two components.

Example 2-1

Random polypropylene (melt flow index (230° C., 2.16 kg): 2.3 g/10 min)(100 parts by mass),tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionato]methane(0.02 parts by mass), 2,6-di-tert-butyl-4-methylphenol (0.1 parts bymass), and an ultraviolet absorber composition prepared in Example 1-8(0.8 parts by mass) were mixed, and the mixture was extruded at 250° C.,to thereby produce pellets. The pellets were injection-molded at 250°C., to thereby prepare test pieces having a thickness of 1 mm.

Comparative Example 2-1

The procedure of Example 2-1 was repeated, except that the samplecompound or the ultraviolet absorber composition shown in Table 2 wasused, to thereby prepare test pieces.

The thus-prepared test pieces were allowed to stand at room temperaturefor three months, and the surface of each test piece was analyzed(initially, and at month 1, month 2, and month 3) by means of a hazemeter (HGM-2DP, SUGA TEST INSTRUMENTS), to thereby determine a hazevalue. Blooming of the test piece was evaluated by the haze value. Theresults are shown in Table 2.

TABLE 2 Bloom test (haze value) Initial Month 1 Month 2 Month 3 ExampleEx. 1-8 43.1 43.9 44.1 44.7 2-1 Comp. Exs. 2-1 UVA-1*⁸ 44.7 45.8 46.047.7 2-2 UVA-3*¹⁰ 48.2 49.9 51.4 55.8 2-3 Comp. Ex. 46.6 47.6 48.1 51.31-4 *¹⁰2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol

As is clear from Comp. Ex. 2-1 to 2-3 in Table 2, test pieces containing2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol,2-(2′-hydroxy-3′,5′-dicumylphenyl)benzotriazole, or a simple mixturethereof exhibited a considerable level of blooming. Particularly, soleuse of 2,2′-methylenebis(4-tert-octyl-6-benzotriazolyl)phenol caused ahigher level of blooming. However, blooming was prevented in the testpieces of Example 2-1 containing a composition prepared throughmelt-mixing.

The precise mechanism explaining why blooming was prevented has remainedunknown. However, one considerable mechanism derived from Examples 1-1to 1-9 is that compositions prepared through melt-mixing show meltingbehavior different from that of similar compositions prepared throughsimple mixing, and such a different behavior may be attributablemolecular interaction during melt-mixing, which is maintained after thecompositions have undergone processing for forming test pieces.

INDUSTRIAL APPLICABILITY

According to the present invention, there can be provided an ultravioletabsorber composition having excellent light resistance and generatingless blooming, and a synthetic resin composition having light resistancethat is remarkably improved by the ultraviolet absorber composition.

1. An ultraviolet absorber composition having a reduced melt temperaturewhich comprises a melt-mixture of a compound (A) represented by formula(I):

and a resin stabilizer (B), wherein the resin stabilizer (B) is at leastone selected from the group consisting of a phenolic antioxidant (b-1),a phosphorus-containing antioxidant (b-2), a hindered amine stabilizer(b-3), and an ultraviolet absorber (b-4) other than the compound (A),and wherein the compound (A) and the resin stabilizer (B) are present inthe melt-blend in an amount to provide a mass ratio (A)/(B) of 95/5 to50/50 sufficient to reduce the melt temperature of the ultravioletabsorber composition.
 2. An ultraviolet absorber composition asdescribed in claim 1, wherein the resin stabilizer (B) is theultraviolet absorber (b-4) other than the compound (A).
 3. Anultraviolet absorber composition as described in claim 2, wherein theultraviolet absorber (b-4) other than the compound (A) is abenzotriazole ultraviolet absorber.
 4. An ultraviolet absorbercomposition as described in claim 3, wherein the benzotriazoleultraviolet absorber is a compound represented by formula (II):


5. A synthetic resin composition comprising a synthetic resin and anultraviolet absorber composition as recited in claim
 4. 6. A syntheticresin composition as described in claim 5, wherein the synthetic resinis a polyolefin resin.
 7. A synthetic resin composition comprising asynthetic resin and an ultraviolet absorber composition as recited inclaim
 3. 8. A synthetic resin composition as described in claim 7,wherein the synthetic resin is a polyolefin resin.
 9. A synthetic resincomposition comprising a synthetic resin and an ultraviolet absorbercomposition as recited in claim
 2. 10. A synthetic resin composition asdescribed in claim 9, wherein the synthetic resin is a polyolefin resin.11. A synthetic resin composition comprising a synthetic resin and anultraviolet absorber composition as recited in claim
 1. 12. A syntheticresin composition as described in claim 11, wherein the synthetic resinis a polyolefin resin.
 13. A method of making a ultraviolet (UV) lightstabilized synthetic resin composition which comprises the steps of: (1)forming an ultraviolet light absorber composition by melt-mixing acompound (A) represented by formula (I):

and a resin stabilizer (B), wherein the resin stabilizer (B) is at leastone selected from the group consisting of a phenolic antioxidant (b-1),a phosphorus-containing antioxidant (b-2), a hindered amine stabilizer(b-3), and an ultraviolet absorber (b-4) other than the compound (A),and wherein the compound (A) and the resin stabilizer (B) are present inthe melt-blend in an amount to provide a mass ratio (A)/(B) of 95/5 to50/50 sufficient to reduce the melt temperature of the ultraviolet lightabsorber composition; and thereafter (2) blending a synthetic resin witha UV light-absorbing sufficient amount of the ultraviolet light absorbercomposition to form a UV light stabilized synthetic resin composition.14. The method of claim 13, wherein the resin stabilizer (B) is theultraviolet absorber (b-4) other than the compound (A).
 15. The methodof claim 13, wherein the benzotriazole ultraviolet absorber is acompound represented by formula (II):


16. The method of claim 13, wherein the synthetic resin is a polyolefinresin.